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Woody community dynamics in two fragments of "cerrado"

stricto sensu

over a seven-year period (1995-2002), MA, Brazil

FABIANA DE GOIS AQUINO

1,3

, BRUNO MACHADO TELES WALTER

2

and

JOSÉ FELIPE RIBEIRO

1

(received: July 5, 2006; accepted: January 4, 2007)

ABSTRACT – (Woody community dynamics in two fragments of “cerrado” stricto sensu over a seven-year period (1995-2002),

MA, Brazil). This study was conducted in two fragments of “cerrado” stricto sensu in the Gerais de Balsas Colonization

Project, located in southern Maranhão, Brazil. The objective was to evaluate the dynamics of the woody plant community, over seven years (1995-2002). Four transects of 160 × 20 m were monitored. All woody plants with a stem diameter ≥ 3 cm, at 0.30 m

above ground level, were recorded. In 1995, 983 and 1,177 stems were sampled in fragments 1 and 2, respectively; in 2002, 1057 and 1406 stems were sampled in the same fragments. In 1995, the Shannon diversity indices (H’) were 3.07 and 3.33, in

fragments 1 and 2, respectively, reaching their maximum value in 2002 of 3.11 and 3.35. The community of fragment 1 showed an increase of 7.5% in density and 4.4% in basal area between 1995 and 2002, while in fragment 2 there was an increment of 19.4% in density and 23.5% in basal area, over the same period. The annual increment in diameter was 0.13 cm year-1 and

0.17 cm year-1 in fragments 1 and 2, respectively. The mortality rate was 2.73% per year in fragment 1 and 4.88% per year in

fragment 2, while the recruitment rate was 3.25% per year and 5.86% per year, respectively. The community presented high recruitment and mortality rates compared to the studies conducted in other sites, indicating a community that was highly dynamic in the period studied.

Key words - fragmentation, permanent plots, plant mortality, recruitment, savanna

RESUMO – (Dinâmica de uma comunidade lenhosa em dois fragmentos de cerrado stricto sensu no período de sete anos

(1995-2002), MA, Brasil). O presente estudo foi conduzido em dois fragmentos de cerrado stricto sensu, no Projeto de Colonização

Gerais de Balsas, sul do Maranhão, Brasil. O objetivo do estudo foi avaliar a dinâmica da comunidade lenhosa no período de sete anos (1995-2002). Foram estabelecidos quatro transectos de 160 × 20 m nos fragmentos, onde foram marcadas todas as plantas lenhosas com diâmetro do caule ≥ 3 cm, medidos a 0,30 m acima do solo. Em 1995, 983 e 1.177 plantas foram registradas

nos fragmentos 1 e 2, respectivamente, e em 2002, 1.057 e 1.406 plantas foram amostradas nos mesmos locais. Em 1995, o índice de diversidade de Shannon (H’) foi de 3,07 e 3,33, nos fragmentos 1 e 2, respectivamente, alcançando o valor máximo em 2002

(3,11 e 3,35). A comunidade do fragmento 1 aumentou 7,5% em densidade e 4,4% em área basal entre 1995 e 2002, enquanto que o fragmento 2 apresentou aumento de 19,4% na densidade e 23,5% em área basal, no mesmo período. O incremento anual em diâmetro foi 0,13 cm ano-1 e 0,17 cm ano-1 nos fragmentos 1 e 2, respectivamente. A taxa de mortalidade foi 2,73% ano-1 no

fragmento 1 e 4,88% ano-1 no fragmento 2, enquanto a taxa de recrutamento foi 3,25% ano-1 e 5,86% ano-1, respectivamente. A

comunidade vegetal estudada apresentou altas taxas de recrutamento e mortalidade comparadas à outros trabalhos conduzidos em diferentes localidades, indicando que se trata de uma comunidade altamente dinâmica no período estudado.

Palavras-chave - cerrado, fragmentação, parcelas permanentes, mortalidade, recrutamento

Introduction

“Cerrado”

stricto sensu is a savanna vegetation

that presents a continuous grass layer overlaid by a

discontinuous tree and shrub layer. This vegetation is

one of the main physiognomies located in the Brazilian

"cerrado" biome (Eiten 1972, Ribeiro & Walter 1998,

Oliveira-Filho & Ratter 2002). Originally, the “cerrado”

biome covered about two million sq. kilometers in the

Brazilian heartland (figure 1) and it is considered one of

the world’s 25 hotspots (Mittermeier et al. 1999, Myers

et al. 2000) partly because of the number of endemic

plants, estimated at about 4400 vascular species, and

partly because it is endangered. This region is

threatened mainly by the high rate of agricultural

expansion throughout native areas, and due to the small

percentage of protected areas (2.5%) (Klink et al. 1993,

Ratter

et al. 1997).

Many studies have provided important information

about the “cerrado” stricto sensu vegetation, detailing

phytogeographical, physiognomic, floristic and

phytosociological patterns (e.g. Ratter & Dargie 1992,

1. Embrapa Cerrados, BR 020, Km 18, Caixa Postal 08223,

73301-970 Planaltina, DF, Brazil.

2. Embrapa Recursos Genéticos e Biotecnologia, Parque Estação

Biológica, 70770-900 Brasília, DF, Brazil.

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Castro

et al. 1999, Felfili et al. 1994, Ratter et al. 1996,

Mendonça

et al. 2000, Ratter et al. 2003). However, it

is also very important to evaluate dynamic changes in

natural vegetation over time to understand the processes

and mechanisms that maintain the community.

Furthermore, this knowledge is important in the support

of conservation programs.

Unfortunately, as pointed out by Felfili et al. (2000),

there is still little information about structural changes

in the “cerrado” stricto sensu vegetation. There is an

absence of information concerning the influence of the

intense agricultural activities on sites of “cerrado”

stricto sensu maintained as natural reserves (fragments

of natural vegetation). Studies of community dynamics

in “cerrado” stricto sensu are essentially restricted to

Silberbauer-Gottsberger & Eiten (1987) in the state of

São Paulo, and Sato & Miranda (1996), Felfili et al.

(2000) and Henriques & Hay (2002) in Brasília, Federal

District, Brazil.

The objective of this study was to evaluate changes

in floristic composition, diversity and dynamic processes

in the woody communities in two fragments of “cerrado”

stricto sensu, in southern Maranhão State, Brazil, over

a seven-year period (1995-2002).

Material and methods

Study area – The study was carried out in two fragments of “cerrado”stricto sensu, located in the Gerais de Balsas

Colonization Project (8º29’ - 8º41’ S and 46º52’ - 46º38’ W), southern Maranhão State, Brazil (figure 1). This Project is part of the Nippon-Brazilian Cooperation Program for Development of the “cerrado” (Prodecer).

The climate of this region is Aw by the Köppen classification, with an average annual precipitation of 1049 mm and average temperature of 26 ºC (from Embrapa “cerrados” dataset). The dry season is from April to October, and the rainy season from November to March.

The Gerais de Balsas Colonization Project was established in 1995, with approximately 35,000 ha. In 1994, before its implementation, 99.7% of the area was composed of native vegetation and the remaining areas were used for subsistence cultivation. In 1995, with the Project in place, half of the area was deforested and converted for commercial agriculture and the remaining area was designated as private reserves - fragments of natural vegetation. This study was developed in two fragments denominated: fragment 1 (3,500 ha) and fragment 2 (1,500 ha) (figure 2). These fragments were monitored from 1995, when the adjacent areas to the fragments were deforested, until 2002.

Fires were registered in both fragments in 1996, 1998, 2000 and 2002. Fragment 2 was intensively burned in 1998.

Continuous inventory – Four transects of 160 m, subdivided into 16 contiguous plots of 10 × 20 m, were established in 1995, with two transects in each fragment. This allowed an area of 1.28 hectares to be monitored. The transects were allocated perpendicular to the edge. They are part of a larger research project that seeks to evaluate the edge effect along 160 meters inside the remaining fragments; for that, contiguous plots that run perpendicular to the edge were used. The first assessment was conducted at the beginning of the wet season of 1995 and the other five inventories occurred in: 1996, 1997, 1998, 2000 and 2002, always in the same season. All woody plants with a stem diameter 3 cm, at 0.30 m above ground level, were recorded, tagged and taxonomically identified (sensuAPG II 2003). Plants were

identified and vouchers were collected and deposited in the Figure 1. Map of Brazil showing the “cerrado” biome distribution and, in detail, Maranhão State with Gerais de Balsas Colonization Project.

Figure 2. Gerais de Balsas Colonization Project with two areas designated as private reserves - fragment 1 (F1) and fragment 2 (F2). („ = “Cerrado” stricto sensu;„ = Gallery Forest;

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Embrapa Recursos Genéticos e Biotecnologia herbaria (CEN), in Brasília, Brazil. A nail in the stem allowed the position for diameter measurement to be standardized in successive assessments. Total height and stem diameter were measured during each survey.

A species list was produced for each fragment studied for each survey. Shannon’s diversity and Czekanowski’s similarity indices were obtained to compare the fragments.

Annual increment in diameter was calculated in each fragment from the average of the differences in increment between the first and last assessments, divided by the study period (seven years).

Mean annual mortality and recruitment rates were calculated using the log-model (Lieberman et al. 1985, Korning

& Balslev 1994, Sheil et al. 1995):

r = (Ct / C0)1/t– 1

where:r is the mean annual mortality (r < 0) or recruitment

(r > 0) rate, t is the elapse of time in years, and C0 and Ct are

the stand sizes at time 0 and after t years, respectively. According to Oliveira Filho et al. (1997) this calculation

allows one to evaluate the respective half-lives and doubling times calculated from the above rate. Half-life [t1/2 = ln(0,5) / ln (1 + r)] is the time required by the community

to decrease its size to half considering the present mortality rate, while doubling time [t2 = ln (2) / ln (1 + r)] is the time taken

to double its size considering the present recruitment rate. Turnover and stability values were estimated from the average of doubling time and half-life, and the numerical difference between them, respectively (Korning & Balslev 1994).

Results

In 1995, 983 and 1177 stems

3 cm were sampled

in the permanent plots of fragments 1 and 2, respectively,

and in the last survey, in 2002, 1,057 and 1,406 stems

were sampled in each fragment. In fragment 1, 48

species were recorded in the first two assessments

(1995, 1996). In 2000, the single individual representative

of

Dimorphandra mollis Benth. died. In 2002, six new

species were registered, Dimorphandra gardneriana

Tul.,

Emmotum nitens (Benth.) Miers, Machaerium

acutifolium

Vogel,

Miconia albicans (Sw.) Triana,

Pterodon emarginatus

Vogel and, Salacia elliptica

(Mart. ex Schult.) G. Don, resulting in a total of 53

species. In fragment 2, 55 species were registered in

the first assessment (1995), and four new species were

included in the next two assessments (1996, 1997):

Casearia sylvestris Sw., Miconia ferruginata

DC.,

Neea theifera Oerst. and

Stryphnodendron

adstringens

(Mart.) Coville. In the 1998 survey,

Casearia sylvestris,

Guapira graciliflora (Mart. ex

J. A. Schmidt) Lundell, Emmotum nitens and Rourea

induta Planch. were not registered in the plots, and in

2000,

Neea theifera,

Stryphnodendron adstringens

and

Couepia grandiflora (Mart. & Zucc.) Benth. ex

Hook. f. were not registered. Finally, in 2002, five species

(Copaifera langsdorffii Desf., Dimorphandra mollis,

Emmotum nitens,

Rourea induta and,

Stryphnodendron adstringens) were included,

resulting in a total of 57 species.

In 1995, the diversity indices were 3.07 and 3.33, in

fragments 1 and 2, respectively, reaching a maximum

value in 2002 in both sites of 3.11 and 3.35. The

Czekanowski index varied from 0.46 to 0.45, indicating

that the sites studied showed qualitative similarity,

although quantitative dissimilarity was shown by the

varying number of individuals of each species between

fragments.

Density and basal area for 19 species with highest

number of individuals in 1995 are given in table 1. In

fragment 1, ten species (Hirtella ciliata,

Erythroxylum

deciduum,

Byrsonima coccolobifolia, Sclerolobium

paniculatum, Davilla elliptica, Byrsonima crassa,

Syagrus comosa, Ouratea hexasperma, Qualea

parviflora

and Pouteria ramiflora) represented 72%

of the total density and 62% of total basal area in 1995.

In 2002, the same ten species contained 72% and 64%

of the total density and basal area, respectively.

Although these ten species have mostly shown similar

percentages over the seven years in relation to density

and basal area, certain species showed considerable

changes in these parameters. For instance,

Sclerolobium paniculatum more than doubled its

density.

Connarus suberosus and Platonia insignis

halved their densities. Salvertia convallariaeodora

increased in density and presented a negative

difference in basal area. This was because one

individual with an 18 cm diameter died, while the

recruitment included individuals with smaller diameter,

close to the lower limit established in the method

adopted.

Ouratea hexaspema,

Mouriri elliptica and

Psidium myrsinoides maintained the same densities

over the seven years.

In fragment 2, ten species (Ouratea hexasperma,

Vochysia rufa,

Qualea grandiflora,

Salvertia

convallariaeodora,

Davilla elliptica,

Sclerolobium

paniculatum,

Connarus suberosus,

Byrsonima

coccolobifolia,

Lafoensia vandelliana and Pouteria

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Table 1. Density (number of stems ha-1) and basal (B.) area (m2ha-1) for 19 species with highest number of individuals in 1995,

in the “cerrado” sensu stricto, Gerais de Balsas Colonization Project, Maranhão, Brazil.

Species in Fragment 1 Family Density Difference B. area Difference

in 1995 2002-1995 in 1995 2002-1995

Hirtella ciliata Mart. & Zucc. Chrysobalanaceae 223 -16 1.614 -0.067

Erythroxylum deciduum A. St.-Hil. Erythroxylaceae 203 -14 0.281 -0.005

Byrsonima coccolobifolia Kunth Malpighiaceae 116 20 0.188 0.072

Sclerolobium paniculatum Vogel Fabaceae Caesalpinioideae 102 103 0.385 0.135

Davilla elliptica A. St.-Hil. Dilleniaceae 94 -23 0.245 -0.020

Byrsonima crassa Nied. Malpighiaceae 88 9 0.391 0.020

Syagrus comosa (Mart.) Mart. Arecaceae 84 -2 0.313 0.046

Ouratea hexasperma (A. St.-Hil.) Baill. Ochnaceae 83 0 0.229 0

Qualea parviflora Mart. Vochysiaceae 56 3 0.567 0.120

Pouteria ramiflora (Mart.) Radlk. Sapotaceae 53 5 0.210 0.042

Myrcia sellowiana O. Berg Myrtaceae 44 -2 0.519 -0.051

Vatairea macrocarpa(Benth.) Ducke Fabaceae Faboideae 34 -8 0.120 -0.040

Mouriri elliptica Mart. Melastomataceae 33 0 0.113 0.018

Psidium myrsinoides O. Berg Myrtaceae 31 0 0.129 0.026

Connarus suberosus Planch. Connaraceae 31 -14 0.060 -0.018

Myrcia ochroides O. Berg Myrtaceae 28 -6 0.086 -0.005

Salvertia convallariaeodora A. St.-Hil. Vochysiaceae 27 3 0.878 -0.121

Platonia insignis Mart. Clusiaceae 20 -9 0.072 -0.046

Rourea induta Planch. Connaraceae 17 -2 0.023 0.001

Others 29 species in 1995 – 169 67 0.733 0.207

Total 1536 7.156

Species in Fragment 2

Ouratea hexasperma (A. St.-Hil.) Baill. Ochnaceae 214 53 0.428 0.073

Vochysia rufaMart. Vochysiaceae 181 31 0.378 0.217

Qualea grandiflora Mart. Vochysiaceae 177 14 0.609 0.087

Salvertia convallariaeodora A. St.-Hil. Vochysiaceae 101 1 1.333 0.176

Davilla elliptica A. St.-Hil. Dilleniaceae 90 59 0.128 0.101

Sclerolobium paniculatum Vogel Fabaceae Caesalpinioideae 81 8 0.228 0.071

Connarus suberosus Planch. Connaraceae 80 11 0.177 -0.026

Byrsonima coccolobifolia Kunth Malpighiaceae 69 16 0.112 0.013

Lafoensia vandelliana Cham. & Schltdl. Lythraceae 67 -12 0.210 -0.029

Pouteria ramiflora (Mart.) Radlk. Sapotaceae 64 1 0.158 0.036

Qualea parviflora Mart. Vochysiaceae 55 45 0.420 0.177

Syagrus comosa (Mart.) Mart. Arecaceae 55 5 0.168 0.008

Eschweilera nana (O. Berg) Miers Lecythidaceae 45 16 0.070 0.052

Tabebuia ochracea (Cham.) Standl. Bignoniaceae 41 6 0.108 0.021

Psidium laruotteanum Cambess. Myrtaceae 39 0 0.159 0.029

Stryphnodendron rotundifolium Fabaceae Mimosoideae 39 -11 0.042 -0.010

Mart. ex Benth.

Erythroxylum suberosumA. St.-Hil. Erythroxylaceae 33 -17 0.031 -0.012

Pouteria torta (Mart.) Radlk. Sapotaceae 30 17 0.049 0.026

Hymenaea stigonocarpa Mart. ex Hayne Fabaceae Caesalpinioideae 28 8 0.047 0.014

Others 36 species in 1995 – 350 151 1.134 0.382

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density and basal area over the seven years. Lafoensia

vandelliana decreased in density and basal area, while

Psidium laruotteanum Cambess. (=Psidium

warmingianum Kiaersk.) maintained the same density

over the seven years. Connarus suberosus increased

in density and presented negative difference in basal

area due to mortality of extremely ramified individuals,

with high basal area values, while the recruitment

included individuals with smaller diameter, close to the

lower limit established in the methods.

In both fragments, the diameter distribution showed

a reversed J-shape, as could be expected in a

continuously regenerating population (figure 3).

Table 2 shows features of vegetation dynamics in

both fragments. The community of fragment 1 showed

an increase of 7.5% in density and 4.4% in basal area

between 1995 and 2002, while in fragment 2 there was

an increment of 19.4% in density and 23.5% in basal

area, over the same period. In terms of density, annual

recruitment exceeded mortality in both fragments.

Consequently, stand half-lives exceeded doubling times.

In terms of basal area, the mean annual growth rate

exceeded the mean annual mortality rate in fragment 2

and the values of those rates were similar in fragment 1

(table 2). Therefore, stand half-lives exceed doubling

times, in fragment 2. Annual recruitment and mortality

varied widely depending on the period analyzed,

particularly in fragment 2 (table 3).

In fragment 1, of the 174 stems that died between

1995 and 2002, 14% belonged to Sclerolobium

paniculatum; 11% to Erythroxylum deciduum; and

10% to Davilla elliptica, while, in fragment 2, 10% of

the 352 dead plants in the same period belonged to

Ouratea hexasperma; 9% to Connarus suberosus;

and 9% to Davilla elliptica. In the 1996 and 1997

assessments, more than 70% of the stems that died

measured from 0.5 to 4 meters in height. Of the 248

recruited plants in fragment 1, 36% belonged to

Sclerolobium paniculatum; 11% to Byrsonima

coccolobifolia and 5% to Byrsonima crassa. Of the

581 recruited plants of fragment 2, 12% belonged to

Davilla elliptica; 12% to Ouratea hexasperma and

7% to Connarus suberosus.

Number of individual

Number of individual

Table 2. Features of dynamics in “cerrado” sensu stricto in

Maranhão, Brazil, during the seven-year study period (1995-2002).

Fragment 1 Fragment 2

Density

Number of plants, 1995 983 1177

Number of dead plants, 1995-2002 174 352 Number of recruits, 1995-2002 248 581

Number of plants, 2002 1057 1406

Mean annual mortality rate 2.73 4.88 (% year-1)

Mean annual recruitment rate 3.25 5.86 (% year-1)

Stand half-life (year) 25 14

Doubling time (year) 22 12

Turnover (year) 23.5 13

Stability (year) 3 2

Basal area

Total basal area, 1995 7.156 5.988

Basal area of dead plants, 1995-2002 1.566 1.030 Basal area increase of surviving 1.704 2.162

plants, 1995-2002

Basal area of recruits, 1995-2002 0.175 0.278

Total basal area, 2002 7.469 7.398

Mean annual mortality rate (% year-1) 3.47 2.66

Mean annual growth rate (% year-1) 3.39 5.00

Stand half-life (year) 20 26

Doubling time (year) 21 14

Turnover (year) 20.5 20

Stability (year) 1 12

Annual increment in diameter 0.13 0.17 (cm year-1)

Figure 3. Diameter distribution in the “cerrado” sensu stricto

of Gerais de Balsas Colonization Project, Maranhão, Brazil. Above: fragment 1; Below: fragment 2. „1995;„ 1996; … 1997;

„ 1998; … 2000 and … 2002.

Diameter

0

100 200 300 400 500

0

100 200 300 400 500 600 700 800 900

3.0-6.0 6.1-9.0 9.1-12.0

12.1-15.0 15.1-18.0 18.1-21.0 21.1-24.0 24.1-27.0 27.1-30.0 30.1-33.0 33.1-36.0

>36.0

3.0-6.0 6.1-9.0 9.1-12.0

12.1-15.0 15.1-18.0 18.1-21.0 21.1-24.0 24.1-27.0 27.1-30.0 30.1-33.0 33.1-36.0

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Discussion

Species such as Hirtella ciliata,

Dimorphandra

gardneriana,

Exellodendron cordatum

(Hook.f.)

Prance,

Myrcia ochroides,

Platonia insignis and

Parkia platycephala Benth. are considered typical

of the north-northeast area of “cerrado” distribution

(Ratter

et al. 1996, 2003), especially in Maranhão State

(Eiten 1994), showing the importance of preserving

areas chosen as private reserves. Although the number

of species has increased in both fragments over seven

years, these species have been represented by only

one or two young individuals, meaning that they

occurred at low density in the plots. Therefore, the

increment in the diversity can be considered transitory,

because any deaths would eliminate these species from

the plots.

The community’s annual increment for fragments

1 and 2, at 0.13 and 0.17 cm per year, respectively, was

similar to that found by Henriques & Hay (2002)

(0.16 cm year

-1

) in the Federal District, Brazil, and lower

than that registered by Silberbauer-Gottsberger & Eiten

(1987) (0.27 cm year

-1

) for “cerrado” stricto sensu in

São Paulo, Brazil. Rezende (2002) found a higher

increment in diameter, ranging from 0.39 to

0.49 cm year

-1

, over a period of eleven years in a

“cerrado”

stricto sensu area in the Federal District,

Brazil, as a consequence of slash and burn. These

studies indicate a low rate of increment in the aerial

parts of plants, which could be associated with poor

soils and long droughts (Henriques & Hay 2002).

Mortality and recruitment rates registered between

1995 and 2002 were high compared to other studies in

different sites in Brazil (table 4). These high rates may

be associated to human disturbances like fire and

fragmentation of native areas, practiced by farmers in

these areas.

Mortality registered in this study was higher than

the rate obtained by Henriques & Hay (2002), in the

Federal District, Brazil. The high mortality rate recorded

may be related to the frequent burning in the study area.

Fragment 2 was intensively burned in 1998, which

possibly caused the high mortality between 1997 and

1998 (11% year

-1

) and high instability. The exclusion of

four species (Casearia sylvestris,

Emmotum nitens,

Guapira graciliflora and

Rourea induta) was

registered in this period. Usually, farmers set fire to

private reserves in an attempt to reduce their size and

use them as supplementary areas for agriculture in the

future; therefore, the natural dynamics of the vegetation

is strongly affected.

Some “cerrado” species may present up to 100%

of mortality after burning (Sato & Miranda 1996,

Hoffmann 1998). Miranda et al. (2003) observed that

frequent burning can modify “cerrado” lato sensu

physiognomies to more open forms, where a larger

number of grassy species appear and favor more intense

and frequent burning. Fire protection favors

fire-sensitive species and increases the abundance of woody

plants in “cerrado” (Moreira 2000).

Additionally, fire may contribute to the high mortality

of smaller individuals, mainly young and juvenile

Table 3. Mortality and recruitment rates in “cerrado” stricto sensu in Maranhão, Brazil, during the seven-year study period

(1995-2002), based on density.

Fragment 1

Period Dead Mortality % year-1 Recruits Recruitment % year-1

1995-1996 19 1.93 39 3.97

1996-1997 26 2.49 24 2.29

1997-1998 18 1.80 22 2.20

1998-2000 81 4.17 32 1.63

2000-2002 30 1.53 131 6.58

Fragment 2

1995-1996 31 2.55 187 15.80

1996-1997 20 1.42 139 10.35

1997-1998 144 11.00 30 0.54

1998-2000 135 5.18 69 2.55

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individuals of the woody flora. Sato & Miranda (1996)

also observed that individuals with stem diameter

between 5 and 6 cm, measured at 0.30 m above ground

level, and total height under 2 m, presented the highest

mortality rates. At the population level, Hoffmann (1998)

showed that fire can cause high mortality in seedlings of

some woody “cerrado” species, such as Miconia

albicans. Therefore, natural mortality on top of fire

impact can affect the structure and composition of

“cerrado” vegetation.

Recruitment rates obtained here were lower than

those registered by Henriques & Hay (2002) for a

“cerrado”

stricto sensu in Central Brazil (table 4).

However, the recruitment rates found by those authors

and in the present study exceed most of those registered

for tropical forests (Korning & Balslev 1994, Phillips &

Gentry 1994) and other “cerrado” studies shown in table

4, mainly in fragment 2, where there was high

recruitment in the 1995-1997 period. One possible

explanation for the high recruitment in the “cerrado”

stricto sensu compared with other physiognomies may

be the high capacity of vegetative reproduction inherent

to many species.

The highest recruitment rate in relation to mortality

resulted from the increase in density from 1995 to 2002.

However, variations were observed in recruitment and

mortality rates when the intervals of one or two years

were analyzed. In fragment 2, this is evident, as in the

1995-1997 periods the high recruitment rates were

followed by high mortality rates. Some studies suggested

that the dynamic equilibrium is characterized by a period

of high mortality followed by another with high

recruitment and so on, maintaining a constant

physiognomy (e.g.

Felfili 1995).

Felfili

et al. (2000) observed that the changes in

density and basal area were larger than those found in

several tropical forests, and this was attributed to the

frequency of disturbances, such as fire, at intervals from

three to five years. However, the maintenance of the

species’ composition, spatial distribution and community

structure in these areas indicated that the studied

vegetation is still resilient. The same can also be said

for the “cerrado” stricto sensu in the study area, where

there were changes in density and basal area, associated

with disturbances. The communities studied presented

high stability, maintaining the original physiognomy during

this period, at least in terms of density and general woody

species composition. The maintenance of floristic

composition and community structure suggests that the

"cerrado"

stricto sensu was resilient to the disturbances

caused by fire and agriculture at least for the

seven-year period studied.

Acknowledgements – The authors are very grateful to Embrapa Cerrados, Campo (Cia. de Promoção Agrícola), Jica (Japan International Cooperation Agency) and Universidade de Brasília (Pós-graduação em Ecologia). In particular we thank José Roberto Rodrigues Pinto and Ernestino Guarino for valuable comments on the manuscript and Nelson de Oliveira Pais, José Ferreira Paixão, Valdeci de Matos Lima and João Benedito Pereira for assistance in the field. This paper is part of a project funded by DIFD and Embrapa Cerrados.

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Table 4. Comparison of the mortality and recruitment rates among some communities of Central Brazil. (CBH = Circumference at breast height, CSL = Circumference at soil level, DBH = Diameter at breast height, DBT = Diameter at the base of the trunk and DSL = Diameter at soil level).

Vegetation Inclusion Mortality Recruitment References

(% year-1) (% year-1)

Gallery Forest CBH≥ 31 cm 3.5 2.7 Felfili (1995)

Mesophytic Seasonal Forest DBH 5 cm 2.6 3.0 Oliveira Filho et al. (1997)

Gallery Forest DBT≥ 5 cm 3.7 2.03 Appolinárioet al. (2005)

Gallery Forest DSL 5 cm 2.1 2.4 Van den Berg (2001)

“cerrado”stricto sensu CSL≥ 15 cm 1.3 11.6 Henriques and Hay (2002)

Mesophytic Forest CBH 5 cm 2.7 3.2 Pinto (2002)

Secondary Forest DBH≥ 8 cm 1.7 3.5 Gomeset al. (2003)

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Imagem

Figure 2. Gerais de Balsas Colonization Project with two areas designated as private reserves - fragment 1 (F1) and fragment 2 (F2)
Table 1. Density (number of stems ha -1 ) and basal (B.) area (m 2 ha -1 ) for 19 species with highest number of individuals in 1995, in the “cerrado” sensu stricto, Gerais de Balsas Colonization Project, Maranhão, Brazil.
Table 2. Features of dynamics in “cerrado” sensu stricto in Maranhão, Brazil, during the seven-year study period (1995-2002).
Table 4. Comparison of the mortality and recruitment rates among some communities of Central Brazil

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